Light-absorbing dyes incorporated in silver halide photographic materials can accomplish a variety of goals, including their use as filter dyes, acutance dyes or anti-halation dyes.
When present in a non-photosensitive top layer or intermediate layer they typically serve as filter dyes eliminating an unwanted part of the light spectrum of the exposure source. A well-known example is the yellow filter layer usually present in colour photographic materials in order to prevent blue light from reaching the green sensitive and red sensitive layers. Another example is formed by UV-absorbing compounds, usually present in the top protective layer, which prevent photochemical deterioration of the image dyes formed by colour development. Examples of useful UV-absorbers include the cyanomethyl sulfone-derived merocyanines of U.S. Pat. No. 3,723,154, the thiazolidones, benzotriazoles and thiazolothiazoles of U.S. Pat. Nos. 2,739,888, 3,253,921, 3,250,617 and 2,739,971, the triazoles of U.S. Pat. No. 3,004,896, and the hemioxonols of U.S. Pat. No. 3,125,597.
On the other hand light-absorbing dyes when present in the emulsion layer can serve as so-called "acutance dyes" or "screening dyes" improving the image sharpness by reducing the sidewise scattering of light by the emulsion grains.
In a third application light-absorbing dyes act as "anti-halation dyes" improving the image sharpness by diminishing the upward reflection of light by the support into the emulsion layer. For this purpose the dye can be incorporated in an undercoat, being a non-photosensitive layer between the emulsion layer and the support, or it can be incorporated in the base itself, or preferably, it can be present in one or more backing layers of the photographic material.
Useful dyes absorbing in the visible spectral region include, for instance, the coloured pigments of U.S. Pat. No. 2,697,037, the pyrazolone oxonol dyes of U.S. Pat. No. 2,274,782, the styryl and butadienyl dyes of U.S. Pat. No. 3,423,207, the diaryl azo dyes of U.S. Pat. No. 2,956,879, the merocyanine dyes of U.S. Pat. No. 2,527,583, the merocyanine and oxonol dyes of U.S. Pat. Nos. 3,486,897, 3,652,284 and 3,718,472, and the enaminohemioxonol dyes of U.S. Pat. No. 3,976,661. Absorbing dyes can be added as particulate dispersions as disclosed in U.S. Pat. No. 4,092,168, EP 0 274 723 and EP 0 299 435.
The dyes incorporated in one or more particular hydrophilic layers of a photographic material may be water-soluble. In this case they are easy diffusible to adjacent layers during coating and drying. For some particular applications, e.g. when serving as antihalation dyes in a sublayer or subcoat positioned between emulsion layer and support, the dyes are preferably non-diffisuble in order to retain a maximal concentration and density in said subcoat. By this is meant non-diffusible under normal coating conditons the pH of the coating solution being neutral or slightly acid depending on the isoelectric point of the gelatin used and the chemical nature of the dye. Under alkaline processing conditions the dye may become diffusable and/or may discolour. Non-diffusable dyes are described in e.g. GB 1.563.809, EP 0 015 601, and a survey can be found in Unexamined Japanese Patent Publications (Kokai) 03-24539, 03-4223, 02-9350, 02-282240 and 03-1133. New classes are recently disclosed in European Patent Publications No's 0 582 753 and 0 587 229.
Light-absorbing dyes must fulfil a number of strict requirements. They should wash-out or decolourize as completely as possible during photographic processing in order to minimize unwanted residual dye stain. When washed-out they or their reaction products should not deteriorate the physical or sensitometric properties of the photographic material during prolonged continuous processing. Moreover, in order to be effective during exposure, the spectral characteristics of incorporated anti-halation dyes or acutance dyes should match as good as possible the spectral sensitivity distribution of the emulsion layer. In its turn this spectral sensitivity distribution has to be tuned to the spectral characteristic of the exposure source.
In pre-press graphic arts particular contact materials exist for quite some time which can be handled in UV poor roomlight. Such so-called Daylight or Roomlight materials are image-wise exposed by means of exposure sources, rich in near UV and short blue light, such as metal-halogen vapour lamps and quartz-halogen sources. Therfore dyes for use in such materials for filter-, acutance- or antihalation purposes must show an absorption spectrum comprised between about 300 to 450 nm with a wavelenght of maximal absorption situated about 350-380 nm.
Prior art on such dyes, which can be called with equal right UV-absorbers since they absorb partially in the near UV and partially in the blue spectral region, is disclosed in e.g. EP 0 252 550, U.S. Pat. Nos. 4,311,787, 4,082,554, 4,053,315, EP 0 519 306, EP 0 524 593, EP 0 524 594, EP 0 529 737, JP-A 03-38636, JP-A 03-13936, JP-A 03-41442, DE 4142935, EP 0 552 010, JP-A 03-48234, U.S. Pat. No. 5,155,015, EP 0 525 445, WO 93/5443, JP-A 03-78741, WO 93/13458, U.S. Pat. No. 4,923,788, EP 0 411 819, JP-A 61-205934, JP-A 01-259358, JP-A 02-73343, JP-A 02-71261 and EP 0 495 406.
It is an object of the present invention to provide a new class of yellow dyes for use in photographic materials and more particularly in graphic arts contact materials.
It is a further object of the present invention to provide a class of yellow dyes with high extinction in the near UV and short blue region and which show low residual stain after processing.